Heat exchanger for an annealing furnace for exchanging heat between two fluids

ABSTRACT

The invention relates to a heat exchanger ( 1 ) for an annealing furnace for exchanging heat between two fluids, comprising a tubular profile which comprises heat exchanger fins on its outside jacket and which is associated on at least one face side ( 3 ) with a connecting flange ( 4 ) with at least one flow opening ( 8 ) for one of the two fluids, especially a hot gas. In order to provide advantageous constructional conditions it is proposed that the profile is a profile tube made of a folded sheet whose heat exchanger fins ( 7 ) aligned in the longitudinal direction of the profile are formed by the corrugated profile, especially the corrugated flanks, of the folded sheet.

FIELD OF THE INVENTION

The invention relates to a heat exchanger for an annealing furnace for exchanging heat between two fluids, comprising a tubular profile which comprises heat exchanger fins on its outside jacket and which is associated on at least one face side with a connecting flange with at least one flow opening for one of the two fluids, especially a hot gas.

DESCRIPTION OF THE PRIOR ART

In the heat treatment of metallic goods to be annealed, the heat treatment and the optionally necessary subsequent cooling occurs under a protective gas, mostly nitrogen or hydrogen, or a mixture of these gases. In order to ensure a proper protective gas atmosphere which is free from impurities and causes oxidation, the supply and discharge of heat usually occurred previously through high-temperature-resistant heat exchangers made of cast materials or ceramic. Hot gases, especially fuel gases or the like, flow through these heat exchangers or recuperators, with the hot gas passing heat to the heat exchanger and the same passes the heat through its outer cooling fins to an annealing chamber or the like. In the known heat exchangers which are made of steel tubes this occurs in such a way that these tubes comprise cooling fins on their outside jacket in order to enlarge the surface area. It is disadvantageous in the known heat exchangers however that they are made of massive heat-resistant material such as cast or ceramic materials, which not only increases the heating time of the heat exchanger as a result of this large thermal mass, but also prevents the application of especially strong dynamic temperature fluctuations as a result of the large heat-storage capacity and reduces the effectiveness of the plant.

Based on the state of the art of the kind mentioned above, the invention is based on the object of providing a heat exchanger for an annealing furnace which is suitable for reproducing highly dynamic temperature fluctuations, as can be required especially in the heat treatment of materials to be annealed.

SUMMARY OF THE INVENTION

This object is achieved by the invention in such a way that the profile is a profile tube made of a folded sheet whose heat exchanger fins aligned in the longitudinal direction of the profile are formed by the corrugated profiles, especially the corrugated flanks, of the folded sheet.

The invention provides an especially simple and cost-effective possibility for producing a heat exchanger which is suitable for an annealing furnace which as a result of its low inherent heat storage capacity can realize especially dynamic temperature fluctuations in the annealing furnace in combination with an especially low material input and thus low weight. Since the profile is a profile tube made of folded sheet, not only the outside jacket surface of the heat exchanger increases in the heat exchanger in accordance with the invention, as is the case in the state of the art, but also the inside jacket surface of the heat exchanger, thus better utilizing the energy contained in the hot gas on the one hand and enabling the realization of higher thermal energy flows with heat exchangers that are of the same size in respect of the state of the art on the other hand. If the same energy quantities need to be transported in relation to the state of the art, the invention offers the advantage that smaller and lighter heat exchangers can now be used. As a result of the lower wall thickness of the heat exchanger in accordance with the invention, the thermal conductivity of the heat exchanger material can virtually be ignored and the efficiency of the heat exchanger increases by a relevant factor.

In order to enable the better utilization of the energy contained in the hot gas and to improve the heat transfer between the fluids and the heat exchanger, turbulators could be associated with the heat exchanger fins on the inside jacket side of the profile tube and/or on the outside jacket side of the profile tube, which turbulators lead to an improved heat transfer by turbulences applied to the fluid flow.

In the simplest of cases, the profile tube can be provided on both face sides with a connecting flange with at least one flow opening for one of the two profiles and a heat carrier fluid flows in the axial direction through the heat exchanger during operation.

As an alternative to this, the profile tube can be provided on one of the two face sides with a connecting flange with at least one flow opening for one of the two fluids, with the other of the two faces sides being sealed. Especially advantageous constructional conditions are obtained when a fluid tube is provided which is coaxial to the profile axis and penetrates the connecting flange and protrudes in the direction of the sealed face side. The heat carrier fluid can be introduced into or removed from the heat exchanger through said fluid tube, which fluid can be removed from the heat exchanger or introduced into the same through a coaxial opening in the connecting flange. Annealing furnaces with heat exchangers that require little space can thus be realized.

The flow opening of a heat exchanger in accordance with the invention is preferably associated with a flue of a burner which is optionally operated with a portion of the preheated heat exchanger exhaust air, which is a portion of the hot gases exiting from the heat exchanger, which is virtually for subsequent combustion.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is schematically shown in the drawings by reference to an embodiment, wherein:

FIG. 1 shows a heat exchanger in accordance with the invention in a longitudinal sectional view;

FIG. 2 shows the heat exchanger of FIG. 1 in a sectional view along line II-II of FIG. 1;

FIG. 3 shows a constructional variant of the heat exchanger of FIG. 1 in a longitudinal partly sectional view;

FIG. 4 shows the heat exchanger of FIG. 1 in an enlarged oblique view.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A heat exchanger 1 for an annealing furnace for the exchange of heat between two fluids, a hot gas 2 flowing through the interior of the heat exchanger and an interior of an annealing furnace to be heated by the heat exchanger comprises on at least one face side 3 a connecting flange 4 with at least one flow opening 8 for one of the two fluids. A flue of a burner can optionally be inserted in said flow opening 8. The heat exchanger 1 is formed by a profile which in accordance with the invention is a profile tube 5 made of folded sheet whose heat exchanger fins 7, which are aligned in the longitudinal direction of the profile tube, parallel to the profile tube axis 6, are formed by the corrugated profile, especially the corrugated flanks, of the folded sheet.

In accordance with the embodiment according to FIGS. 1 and 2, the profile tube 5 is associated on both face sides with a connecting flange 4 with at least one flow opening 8 each for one of the two fluids which flow through the profile tube 5 in the direction of the profile tube axis 9 in operation.

According to the embodiment of FIG. 3, the profile tube 5 is associated on one of the face sides with a connecting flange 4 with a flow opening 8 for one of the two fluids and the other of the two face sides is sealed with a sealing plate 10. Moreover, a fluid tube 11 is provided which is coaxial to the profile tube axis 9, which penetrates the connecting flange 4 and protrudes in the direction of the sealed face side, towards the sealing plate 10. The hot gas is introduced into the heat exchanger 1 via the fluid tube 11 and leaves the same through a coaxial annular gap between the fluid tube 11 and the connecting flange 4 through the flow opening 8.

The heat exchanger 1 is produced by folding sheets with welded end pieces, with the folding occurring without any extension on the longitudinal sides of the profile surfaces. 

1. A heat exchanger for an annealing furnace for exchanging heat (1) between two fluids, comprising a tubular profile which comprises heat exchanger fins on its outside jacket and which is associated on at least one face side (3) with a connecting flange (4) with at least one flow opening (8) for one of the two fluids, especially a hot gas, wherein the profile is a profile tube (5) made of a folded sheet whose heat exchanger fins (7) aligned in the longitudinal direction of the profile are formed by the corrugated profile of the folded sheet.
 2. A heat exchanger according to claim 1, wherein turbulators are associated with the heat exchanger fins (7) on the inside of the profile tube jacket and/or the outside of the profile tube jacket.
 3. A heat exchanger according to claim 1, wherein a connecting flange (4) with at least one flow opening (8) for one of the two fluids is associated with the profile tube (5) at both face sides.
 4. A heat exchanger according to claim 1, wherein a connecting flange (4) with at least one flow opening (8) for one of the two fluids is associated with the profile tube (5) at one of the two face sides and the other of the two face sides is sealed.
 5. A heat exchanger according to claim 4, wherein a fluid tube (11) is provided which is coaxial to the profile tube axis (9) and which penetrates the connecting flange (4) and protrudes in the direction of the sealed face side. 